In the field of body exercise and strength training, there is a need to exercise the lower extremities under a resistive load. Various exercises have been devised to strengthen hip and leg muscles of the body through squatting exercises and leg lifting exercises. To increase the exercise level, the person performing the exercise may carry weights on the shoulders while doing squatting exercises. However, squatting exercises place great stress on knee joints, ligaments, and tendons, and can lead to injury if not performed properly and with care. In addition, the use of carried weights to further load the musculature presents the problem of reduced stability with a raised center of gravity which occurs when a barbell is placed on the shoulders.
Some exercise machines nave been devised to facilitate exercise of leg muscles under load. The known devices fail to vary the load between stages in the exercise when the body is weaker such as at the bottom of a squat maneuver. A need exists for an exercise machine which can be safely used to effectively resist the action of the lower extremity muscles and thereby to provide strengthening while providing a load which varies between positions during the exercise.